Usually, a magnetic head assembly for storing and retrieving data from a magnetic disk has an openable, hinged side to permit insertion of a magnetic disk. When such a disk is inserted, an arm is swung to its closed position. Then, storing or retrieving of data is allowed. Under this condition, a certain force is applied to one magnetic head to bring the head into sliding cnntact with the disk. The force applied to the head is adjusted by adjusting the force applied from the arm to the carriage, whether the disk is a single- or double-sided recording medium.
One example of such a magnetic head assembly is shown in FIGS. 3 and 4. This assembly comprises a carriage 2 having a lower magnetic head 1 at its front end and an arm 4 having an upper magnetic head 3 that is disposed opposite to the lower head 1. The arm 4 can be swung upwardly by a leaf spring 5 hinged at a location remote from the heads. The arm 4 is mounted to the carriage 2 at the base, indicated by 11, of the carriage 2 remote from the heads, by a screw 13 via a retainer member 12.
In order to bring the magnetic head 3 into sliding contact with a disk 6 with an appropriate force as mentioned above, one end of a tension spring 7 is attached to the arm 4. The other end of the spring 7 is fixed to one end of an adjusting member 8 mounted on the bottom of the carriage 2. The side surface of the adjusting member 8 bears on the tip of a protrusion 9 formed on the bottom of the carriage 2, so that the adjusting member 8 can swing. A male screw 10 is screwed to the other end of the adjusting member 8. Thus, the adjusting member 8 is held to the bottom of the carriage 2. The screw 10 mounted on the upper side of the carriage 2 supports the adjusting member 8 from above it in such a way that the adjusting member can be adjusted. That is, the adjusting member 8 can be swung about the tip of the protrusion 8. Thus, the tension on the spring 7 can be adjusted.
The arm 4 is mounted to the carriage 2 at the position of the base 11 as mentioned above. The position of the arm 4 relative to the disk 6 is determined by the height at which the upper head 3 bears on the lower head 1 and also by the height of the surface of the arm 4 facing the carriage 2 above the carriage, the arm 4 being raised by a protrusion 19 formed on the carriage 2 on the side of the base 11. When the arm 4 is swung upwardly, a portion 30 of the arm 4 that is close to the base 11 bears on the prttrusion 19 on the carriage 1. The arm 4 rotates about this portion 30 through a certain angle, as shown in FIG. 3.
The magnetic head assembly constructed as described above is equipped with the two magnetic heads 1 and 3 which are attached to the carriage 2 and the arm 4, respectively, whereby data can be written to, or read from, both sides of the disk 6. The positions of the gaps in the heads 1 and 3 are accurately adjusted in such a way that the distance between them is 4 tracks when the track density is 48 TPI and 8 tracks when the density is 96 TPI. In this way, the disk 6 can be replaced with the other kind of disk.
One method presently frequently adopted for mounting the arm 4 to the carriage 2 is to tighten the screw 13 via the retainer member 12 while watching the distance between the positions of the gaps in the heads 1 and 3 (in reality, the positions of the cores are used instead) with a microscope.
Another method presently commonly adopted consists in retrieving data from the disk by the use of a disk for adjusting the gap positions and in tightening the screw 13 via the retainer member 12 while adjusting the position of the arm 4, until the obtained output signal reaches a certain level.
In either case, the arm 4 is attached to the carriage 2 with the screw 13. Even if the position of the arm 4 is accurately adjusted relative to the position of the carriage 2, a torque is exerted between the leaf spring 5 and the screw 13 when the screw 13 is tightened. As a result, the spring 5, hence the arm 4, is displaced from the intended position, although slightly. Another problem resides in the fact that after the tightening the stress stored in the carriage 2 and the leaf spring 5 is released, causing a displacement. These problems have deteriorated the manufacturing yield, increasing the cost to manufacture the product.